Don't sweat this. Don't think of dinos as a "pest" that can be quarantined or killed off forever. Some amount of them are always going to be present in a diverse microbiome. They are just outcompeted by hundreds over other specie of bacteria, algae, coralline, films, etc.
I could dump a bucket of live dinos in my systems and you would never know it visually. They only thrive when we starve (or kill with Chemiclean) the other surface competitors. I think of dinos as scavengers, waiting for us to scorch the earth so they can multiply by consuming the dead or weakened microscopic competition.


